Venous thromboembolism (VTE) is caused by a combination of blood hypercoagulability, endothelial dysregulation, and blood stasis. This biologic dysregulation has environmental and inherited sources that interact to modulate thrombotic risk. Female sex-hormone-based oral contraceptives (OCs) are an important environmental cause of thrombosis in young women, increasing the risk of VTE 2 to 4-fold. Ultimately, a pre- menopausal woman?s risk of VTE is multifactorial: no single inherited or environmental factor satisfactorily explains why some women who use OCs are at greater risk of a thrombotic event than others who use OCs. Assessing thrombotic risk in women before initiating OC use can help identify women who may be at higher risk of a clinical event. A risk-prediction model should account for the diverse and unique biology of each woman and how it responds to the challenge of OC hormones. The aim of this application is to elucidate mechanisms by which exogenous female sex hormones (OCs) increase the risk of VTE in premenopausal women. Over the course of the 2-phase project, we will develop and expand a model system that accounts for individual-specific and hormone-specific variables and that can be used to predict risk of thrombosis in women using OCs. Our approach is to use panomics technology to discover biology relevant to VTE in premenopausal women using OCs, and to apply panomics findings to understand the functional effects of OCs on vascular cells and blood composition. Our proposal has 4 aims, which will drive biologic discovery and functional experimentation. R61 Overview: Discovery. We will identify new genes, protein markers, and biologic pathways associated with OC use and VTE risk using ?panomic? resources (genomic, transcriptomic, and proteomic) and functional cell biology and biochemistry techniques. Aim 1: Identify novel genes that contribute to VTE in premenopausal women using OCs in 3 well- characterized, case-control studies of VTE. Aim 2: Characterize effects of OCs on endothelial cell (EC) transcriptomic and proteomic responses, EC procoagulant activity, and ability to promote clot formation. R33 Overview: Validation and Functional Testing. We will validate candidate genes and proteins identified in the R61 phase, characterizing their function in an in vitro cell-based model of coagulation. We will characterize interactions between EC dysregulation and plasma hypercoagulability to promote the formation of prothrombotic clots in a blood-endothelial interface model. Aim 3: Characterize candidate genes and proteins in human populations, focusing on Aim 2 discoveries. Aim 4: Characterize the novel candidate genes identified through discovery and validation in the aims above, and determine effects of each gene on EC procoagulant activity in normal and hypercoagulable plasmas. Collectively, these aims integrate discovery and functional-analysis information to identify biologic variation that promotes OC-induced VTE. This study will yield functionally-validated molecular signals and a blood- endothelial interface model for incorporation into VTE risk prediction tools in premenopausal women.